The invention relates to a rotary oil feedthrough for sealing off a pressurized oil compartment between a rotatable shaft and a shaft mount, where the rotary oil feedthrough displays a radial oil passage for connecting an oil duct of the shaft and/or the mount to the pressurized oil compartment in fluid-permeable fashion, and has a seal arrangement that seals off the pressurized oil compartment on both sides in the axial direction of the shaft.
Generic rotary oil feedthroughs are put to diverse uses, mainly in applications involving a rotary hollow shaft whose cavity forms an oil duct. In this context, the space between the shaft and the mount assigned to it is filled with oil that is usually pressurized. Where appropriate, the mount surrounding the shaft can in turn be connected to the oil-containing pressurized compartment between the shaft and the mount in fluid-permeable fashion, and the mount itself can generally be designed as a hollow shaft. The oil ducts of the shaft and the mount can be connected in fluid-carrying fashion via the pressurized oil compartment. The pressurized oil compartment between the shaft and the mount is axially sealed off towards the outside by two separated sealing rings that are thus located on both sides of the oil supply ducts of the shaft and/or the mount running into the pressurized oil compartment. Rotary oil feedthroughs of this kind can be used in transmissions, but also for other applications.
The rotary oil feedthrough must satisfy stringent tightness requirements, even at high relative speeds of the shaft in relation to the mount, high pressures or pressure fluctuations, and high temperatures or temperature fluctuations. Up to now, rectangular rings made of steel or plastic have mostly been used as the sealing rings on rotary oil feedthroughs of this kind, since the otherwise customary lip seals cannot be considered because of the high operating temperatures. For sealing in relation to the respective components, the rectangular rings are hydraulically pressed against these components. The axial (lateral) boundary surface of the sealing ring then lies under hydraulic pressure on the groove flank of the component receiving the sealing ring. At the high rpm speeds to which shafts used with rotary oil feedthroughs of this kind are usually exposed, this results in substantial frictional forces on the sealing ring, which lead to substantial temperature increases on the friction surface or the sealing surface of the sealing ring. Cooling with leakage oil is necessary to avoid overheating of the respective components on the friction surfaces. However, at very high oil pressures—and thus high contact pressures of the sealing ring on the sealing surface of the respective component—and high relative speeds, the result of this is that a relatively large quantity of cooling oil is needed as the leakage flow, meaning that the actual function of the seal arrangement is significantly impaired. Since a large number of rotary oil feedthroughs may be present in a machine, such as a transmission, the overall frictional losses of the individual rotary oil feedthroughs also lead to significant performance losses of the respective machine, such as a motor with transmission.
The high relative rotational speeds of the sealing ring in relation to the components lying on it in sealing fashion are particularly critical as regards the tightness of the rotary oil feedthrough, meaning that excessive relative speeds must be avoided. On the other hand, the relative speeds have a major influence on the design of the sealing ring receiving groove, the surface quality of the sealing surfaces, and the material quality and hardness of the components in the region of the sealing surfaces. As a result, it is often necessary to use hardened materials in the region of the sealing surfaces. If, for example, aluminum shafts or mounts are used, the respective sealing surfaces usually have to consist of hardened, e.g. anodized, aluminum in order to have sufficient durability. Furthermore, the grooves, against the groove flanks of which the sealing ring can be positioned in sealing fashion, usually have to be of relatively small design, in which context it is usually difficult to gain access to the groove flanks, meaning that their machining is then also complicated. It is then generally also difficult to check the quality of manufacture of the sealing surfaces.
Furthermore, rotary oil feedthroughs of this kind are supposed to display good response characteristics, i.e. the oil leakage should be minimized as soon as possible when the oil pressure rises. This is only possible within limits on conventional rotary oil feedthroughs.